Backpressure with a 3inch pipe

[S14Swap240sx]

Hey everyone, one the ka24de, if you have hotshot headers and then a 3inch test pipe with a 3inch apexi n1 exhaust, are u just about ready to start loosing power?

[InsanityInc]

Backpressure is never good. If you really want an explanation as to why, and why too large of a pipe causes a power loss, ask and I'll give it to you, but I'm tired of writing it.

A 3 inch pipe has been shown to have no losses on a KA, and very substantial gains.

[S14Swap240sx]

ok thanx for the quick response.. i was gonna sell my exhaust for a 2.5inch but i guess now it can stay for a lil longer =)

[InsanityInc]

the only reason to go smaller is if you think it's too loud. That can be fixed by adding a resonator and/or a different muffler. I bet yours probably has one of those dumb straight through ones that don't reduce the sound at all?

[S14Swap240sx]

yes it is strait threw, but im not worried about the sound

[drftnassmofo]

if you've got other mods that add hp besides the headers then 3" all the way back would it be better to go w/ 3 or 2.5..and if u dont have other performance mods will it cause a torque loss and actully make you slower???oes anybody know for sure??

[InsanityInc]

If you aren't worried about the sound, then why would you go to a smaller pipe?

Quote »if you've got other mods that add hp besides the headers then 3" all the way back would it be better to go w/ 3 or 2.5..and if u dont have other performance mods will it cause a torque loss and actully make you slower???oes anybody know for sure??[/quote]It doesn't cause any losses to put a 3" on a KA. There are some dynos floating around, if you want to look for them.

[masticatingcow]

While I haven't yet found those dyno sheets he speaks of, if InsanityInc is right, then this is great news for those of us KA guys who want to eventaully get some turbo going, but don't want to waste money on upgrades that will eventually get replaced.

If anyone finds those dynos that prove you lose little to no torque with a 3" pipe, please post links. I know I will.

[Quach]

While I haven't yet found those dyno sheets he speaks of, if InsanityInc is right, then this is great news for those of us KA guys who want to eventaully get some turbo going, but don't want to waste money on upgrades that will eventually get replaced.

If anyone finds those dynos that prove you lose little to no torque with a 3" pipe, please post links. I know I will.

hey i have a link to the dyno charts. i was actually thinking of 3'' piping myself, but my decision is still up in the air. ive heard of people putting cat backs on and losing power, so im gonna look into it a bit more before i make a final decision. my main worry is that putting such a free flowing exhaust may change the power curve of the car, i would like more top end power, but i dont wanna sacrifice low end for it. can anyone give me some feedback on this? does anyone have a video or sound clip of a n/a ka24de with headers to 3" piping, or any n/a ka24de with some exhaust work done? im curious of the sound these cars make when opened up (...and fireballs...).

[180fan]

That dyno chart can't be applied as proof of 3" working well on a KA. It's for a specific exhaust. There are exhausts out there that are made so poorly you might see some gains, then again you might not. Even when buying an exhaust, buying into big names isn't a guarantee. Example, the 350z had big name companies making exhausts, but only a few if I remember correctly, made power, Nismo being one, and the other one being Greg's own BRM. Look around for more dyno charts instead of just applying the Proracer's dyno chart to everything under the sun.

[ddgsxr504]

Well after reading all these comments it's safe to summise that, 1. You are making anywhere from 10-20hp from your Apexi N1 and 2. if you want it to be quieter, don't downsize your pipe or add a resonater because those usually make you car sound like $#!%, get a baffle that fits into the tip of the cannister.

[URM S14]

what people dont pay attention to is the dyno is of a cat back and nothing else. that means it still has the stock cast iron header and tons of backpressure from it. Im sure once a hotshot header is used, that you will most definately see power lose in the low end but also see more top end. backpressure is touchy subject here ive noticed. But there IS too big.

Velocity is the key factor. The reason that you see an 80mm catback add that much power on a KA is because of the displacement of the engine being 2.4 liters. and thats a ways up from the 1.6-2.0 most 4-bangers are.

ive done plenty of my own research and ive decided on the BRM 2.5" piping.To each his own though

[eddiec]

heres a link to a short clip. what your hearing is hotshot headers to a 2.5 catco cat to a 2.5 dynomax muffler. http://nissaninfiniticlub.net/...V.MPG ive changed it since to just the muffler. its very loud, but this is not a street car so it doesn't really matter.

[1991S13]

Heres a good link about exhaust in general...http://www.nsxprime.com/FAQ/Mi...y.htm

I like to believe how they put it: "bigger is better" does not apply to exhaust. You need pipe large enough to reduce backpressure, but theres a downside. If the pipe is larger, there is more room for the exhaust. Since there is more room, the exhaust has more room to cool down before it is pushed out. Cool air is denser than hot air, so when it cools down and expands this creates backpressure. Anyone follow me? It sounds like it makes sense, so thats why I follow that theory lol. But the whole article on that site is worth a read.